I'm not sure I'd so readily agree with this statement. (Perhaps you're being sarcastic!...) But notice that the rules at issue (at least for BIZ and NAME, though not for US) result from contracts between ICANN and the respective registry operator. In this context, it's not hard to see why ICANN would properly have an interest here.

Just tell me why it's necessary to rescind something by "community consensus" which wasn't created by "community consensus" in the first place?

One would like to imagine that the new TLD creation system reflected a rough consensus of sorts -- in the DNSO (via evaluation guidance from the NC, and specific comments from the constituencies and GA members), in public comments subsequently solicited, etc. Certainly there are questions about how true the results were to the various stages of this process -- various folks wanted the situation to turn out differently than it ultimately did. But I think it's fair to say that the process, including the registration restrictions, generally reflected comments received from interested members of the Internet community. If a clear consensus were to develop -- here, in the GA, across constituencies and in the NC, etc. -- that these rules ought properly be modified in some way, I suspect ICANN and the registries would take such comments to heart.